The present invention relates to a technology for developing a seat belt retractor to be installed in a vehicle.
Conventionally, seat belt apparatuses of various structures for restraining an occupant in a vehicle by a seat belt are known.
Japanese Unexamined Utility Model Publication No. H06-71333 (“JP Pub. No. '333”), which is incorporated by reference herein in its entirety, discloses a structure of a seat belt apparatus capable of winding and unwinding a seat belt by the driving of a motor or the like. With the technology disclosed in JP Pub. No. '333, a seat belt retractor employs a structure in which the winding and unwinding of the seat belt onto a spool is conducted by a motor and a structure in which the tension on the seat belt is intermittently changed so as to change the restraining force by the action of the motor, thereby warning a driver about the possibility of a vehicle collision.